23 
mens a small tubercle may be observed on the back portion of each 
eve. 
•/ 
Ocelli .—These are minute simple eyes placed on the front of the 
head ; there are usually three of them, but are very difficult to find 
even with a microscope. 
Thorax. 
This forms the middle portion of the body, and supports the legs 
and wings when present, and is composed of three pieces, the front 
portion or ring is the Prothorax , and supports the front pair of 
legs; the Mesothorax or middle portion bears the middle pair of legs 
and also the front or upper wings when present; the Metathorax is 
the hinder portion to which the abdomen is attached, and bears 
the hind pair of legs and the hind or under wings when present. 
The Prothorax or first segmemt behind the head, is connected with 
the head by “ a dense membrane which shows itself often as a light 
colored band” (Buckton). It is usually smaller than the following 
segment, and narrower than the head; but an exception to this rule 
occurs in the case of the winged Chermes , which has this division 
developed until it is nearly or quite. as large as the mesothorax. The 
upper side or dorsal surface is the Pronotum , the under surface the 
Prosternuiu , though these terms are seldom brought into use in de¬ 
scribing species of this family. As before stated this division supports 
the first or anterior pair of legs, which are attached to the underside; 
the points of attachment being sometimes designated as the Patera. 
The Mesothorax- or second segment behind the head, is usually much the 
largest and most conspicuous portion of the thorax, bearing the second 
or middle pair of legs, and the upper or fore-wings, when present; 
in some wingless and especially subterranean species there is scarcely 
any difference in form between the segments which form the thorax 
and those which form the abdomen, as may be seen by reference to 
fig. 32—( Tychea. panici , Thos?). The upper surface— Alcsonotnrn, which 
is sometimes spoken of as the disk of the thorax, in the winged 
specimens usually presents three conspicuous lobes or rounded tuber¬ 
cles; these are sometims black, while the rest of the thorax is green as 
may be seen in some specimens of Aphis mali. The underside or 
Mesosternum is deeply excavated to receive the folded beak. 
Winys .—These organs are of the highest importance in determining 
species, as they enable us more easily than any other character to de¬ 
termine the genus or group to which a specimen belongs. 
The front or upper pair is usually much larger than the hind pair, 
and the former are generally connected with the latter by a minute 
compound hooklet situated on the front or costal margin of the latter. 
They are usually very delicate and membranous, and mostly transpa¬ 
rent, though occasionally dimmed by smoky or fuscous patches. 
As a very general rule some individuals of each species at some 
time during the season acquire wings, but there are a few subterra¬ 
nean species which do not, so far as known, present winged indi¬ 
viduals. In most species, the wings, during repose, are placed nearly 
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